The present invention relates to a composition for coating materials and an antifouling coating composition to be used for preventing attachment of marine organisms to the underwater or submarine structures such as ships, fishing nets, drainage conduits, etc.
Numerous species of marine organism, such as barnacle, ascidian, serpula, mussel, laver, etc., live in the seawater. When a structure such as a ship, fishing net, drainage pipe, etc., is set or placed in commission in or on the sea, the marine organisms cling to the structure and grow to give various kinds of damage to the structure. For instance, if the ship's bottom is incrusted with marine organisms, the frictional resistance of the seawater increases to cause a reduction of cruising performance of the ship, so that if it is tried to keep a constant cruising speed of the ship, its fuel consumption increases to pose a serious economical problem. Also, if the marine organisms cling to the fishing net used for ocean culture, the meshes of the nets would be clogged up, which could prove fatal to the cultured fishes and shellfishes.
Hitherto, in order to prevent attachment of the marine organisms to the underwater structures such as mentioned above, antifouling paints using homopolymers or copolymers of organotin-containing unsaturated monomers as resinous component (see Japanese Patent Examined Publication (JP-B) Nos. 40-21426, 44-9579, 46-13392, 49-20491, 51-11647, 51-12049, 52-48170, etc.) have been applied to said structures. These polymers have their organotin portion hydrolyzed with the seawater (pH: 8.0-8.3). As a result, not only the organotin serves as an antifouling agent, but also the polymer surface which has been made soluble in seawater is gradually eroded by the moving seawater to bare out the new coating surface, thus producing a long-lasting stabilized antifouling effect. However, the organotin released into the seawater from the paints is hard to decompose and may be taken in by and accumulated in marine organisms and, through the food chain, it may get into the human system. This involves the possibility of causing serious physical trouble such as deformity. So, use of the dangerous organotin compounds has been restricted.
Request is now voiced in the art for the development of a resin for antifouling paints which are capable of producing a long-lasting stabilized antifouling effect, in place of the highly dangerous organotin-based resins. Ideally speaking, it is desirable that the resins used for antifouling paints are of a hydrolyzable type like the organotin-based resins and have ability to form coating eroded gradually during usage in the seawater, but proposals involving use of hydrophilic or water-repellent resins have also been made (Japanese Patent Unexamined Publication (JP-A) Nos. 62-290768, 62-13471, 58-180565, 57-67672, etc.). However, it is hardly possible to realize a long-lasting stabilized antifouling effect by use of a resin having the hydrophilic or water-repellent properly alone.
In view of the above, various hydrolyzable resins having a specific carboxylic acid ester in the side chain have been proposed (W0 84/02915, JP-A Nos. H2-69576, 63-215780, 62-57464, JP-B Nos. 55-39271, 61-3830, etc.), but their effect has not been well satisfactory.
On the other hand, JP-A No. 2-99567 proposes to use copolymers of maleic anhydride derivatives while JP-A Nos. 51-124130, 62-135575 and 62-501293 propose use of copolymers of the derivatives having free carboxyl groups for said purpose. These copolymers have no toxicity unlike the organotin-based resins and are expected to have excellent ability to form coating eroded gradually during usage in the seawater.
However, these copolymers, when used in anti-fouling paints, had fatal defects in that as they are mixed with a copper compound which is treated currently as a toxicant, the paint could cause thickening-gelation during storage, and that the ability to form coating eroded gradually during usage in the seawater is poor.